Hydrogels have had a profound impact in the fields of tissue engineering, drug delivery, and materials science as a whole. Due to the network architecture of these materials, imbibement with water often results in uniform swelling and isotropic expansion which scales with the degree of cross-linking. However, the development of internal stresses during swelling can have dramatic consequences, leading to surface instabilities as well as rupture or bursting events. To better understand hydrogel behavior, macroscopic mechanical characterization techniques (e.g.\ tensile testing, rheometry) are often used, however most commonly these techniques are employed on samples that are in two distinct states: (1) unswollen and without any solvent, or (2) in an equilibrium swelling state where the maximum amount of water has been imbibed. Rarely is the dynamic process of swelling studied, especially in samples where rupture or failure events are observed. To address this gap, here we focus on rupture events in poly(ethylene glycol)-based networks that occur in response to swelling with water. Rupture events were visualized using high-speed imaging, and the influence of swelling on material properties was characterized using dynamic mechanical analysis. We find that rupture events follow a three-stage process that includes a waiting period, a slow fracture period, and a final stage in which a rapid increase in the velocity of crack propagation is observed. We describe this fracture behavior based on changes in material properties that occur during swelling, and highlight how this rupture behavior can be controlled by straight-forward modifications to the hydrogel network structure.
Pinned Boundaries Delay Contraction and Shape Stress Relaxation in Active Gels
School of Physics and Astronomy, Rochester Institute of Technology（罗切斯特理工学院物理与天文学学院）；Department of Physics and Biophysics, University of San Diego（圣地亚哥大学物理与生物物理系）
NANOG assembles into self-limiting aging micelles that drive a sol-gel transition and modulate DNA dynamics
Centre for Regenerative Medicine, Institute for Regeneration and Repair（再生医学中心，再生与修复研究所）；School of Physics and Astronomy, University of Edinburgh（爱丁堡大学物理与天文学院）；School of Molecular Biosciences, University of Glasgow（格拉斯哥大学生物分子科学学院）；Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh（爱丁堡大学生物科学学院干细胞研究所）
